Scavenging tappet



July 14, 19 6- J. 1.. TAYLOR SCAVENGING TAPPE Filed Dec, 24, 1931 F- 5.far

INVENTOR'. Jbfin Leonard Fly/a1:

AT RNEY.

Patented July 14, 1936 UN I TE D STAT ES ATE NT O-FF' 9 Claims.

This invention relates to valve tappets for use particularly inoil-burning engines, or other internal combustion engines.

Anobject of the invention is to generally improve the constructionandoperation of devices of this class.

A further object is to provide for the impositive actuation of a valve,and further objects are to provide the following:

A valve actuating device of a collapsible nature arranged to storeenergy from: a cam for later actuation of a valve.

A device arranged for actuating a valve in response to both a cam, andthe pressure in the cylinder controlled by the valve.

An extremely simple cam mechanism which will vary the timing of ascavenging air valve in response to cylinder conditions.

A device which will provide for reversing. an engine without specialreversing mechanism.

An arrangement for actuating a plurality of. valves at differentdistances from a rocker arm.

Qtherexpe'dients for the practicev of the invention, and theaccomplishment of the. above objects.

The means and manner of accomplishment of these objects are fully setforth in thefollowing specification and accompanying drawing in which:

Fig. 1 is a.sectionalelevationtaken online |-l' of Fig. 2.

Fig. 2 is a top plan of Fig. 1, drawn to' a reduced scale.

Figs- 3, 4, and 5 are perspective views or parts and assembliesindicated in Fig.1-

Fig. 6 is a. modification of a rocker arm element.

Similar reference characters apply to. like parts Ehroughout. theseveral views and the specifica- Applicant has devised. atappet for atwostroke cycle engine in which. the scavenging air is introducedthrough the cylinder head through appropriate volves while the exhaustgases are discharged through ports opened by the piston at the bottom ofits stroke. In' this type of engine the cylinder pressure will behighest when the piston is approximately at top dead center, but it willdiminish progressively as the piston recedes and expansion of thecontents of the cylinder takes place. As the exhaust port opens nearbottom dead center there will ordinarily be a decided drop in pressure,and it is at this point where the exhaust pressure falls below a predc--terminedvalue that it is desirable to have the scavenging air' admitted.

It is: undesirable, however, to have the valves open before: thepressure has been reduced to a value below, or at least equal to that ofthe 5 scavenging air supply, since otherwise some of the exhaust gaseswould be forced into the air supply an'd'later returned to the engine todilute the fresh air.

Applicant has devised a construction in which 10 the valves are operatedby a cam, but impositively so that if at the time that the cam wouldopmate the valves the cylinder pressure is higher than desired, theresulting resistance to movement of the valves will maintain themclosed, and they will open: subsequently to the action of the cam whenthe exhaust port has been open long enough to reduce the pressure in thecylinder tothe desired value; the valves being allowed by the 0am toclose at the most desirable" point in the cycle.

The closing point would preferably be slightly after the closing pointof the exhaust port in order togive a slight supercharging effect, as isdesirable in this type of engine, and in the event of reverse rota-tion,the fall of the cam becoming therise, theva'lves would be opened tooearly if it were not for the impositiveor yielding actu-' atingvmechanism, which as above explained permits the valves to remain closedbeyond the point of actuation by the cam. In laying out the cam,therefore, all that need be considered is the desired closing points,and these may be made correct for engine operation in either direction,the opening movement taking place automatically at the. correct point inthe cycle, andreversal of the engine being accomplished without shiftingthe cam or making any changes except in the time of combustion.

Referring to the drawing, and particularly 40 Figs. 1 and 2, R is acompound rocker whose pivotalshaft or fulcrum P, is disposed in familiarmanner between air valves and tappet' assemblies, the latter beingarranged in suitable relation to a cam-shaft for actuation thereby. Thescavenging-air valves are here indicated by their stems S-S", whichextend upwardly through an air manifold M, a portion of which is shownin Fig. 1. I

In the illustrated embodiment the valve stem or stems are pressed downby the rocker, and returned by springs such as Sp, interposed be tweenmanifold M and washers'or abutmentsW disposed about the stems and heldin place by means of pins Pi in the stems.

The rocker has arms RI and the singular arm R2 oppositely extending fromthe fulcrum P, the rocker being provided with a bearing constructionincluding caps rr integral or otherwise fixed with a spacing half-sleeveR3 which encloses the aforesaid shaft P. The arm R2 has a socket portionto receive the spherical head I of a push rod 2 provided with anadjusting nut 3, also provided with a spherical head that rests in asimilar socket formed in the upper end of a hollow reciprocating stem 4,axially central in the novel tappet means here concerned. The elementsI, 2 and 3 form a thrust-link that is free to accommodate itself to thearcuate swing of the rocker arm R2 which occurs due to the reciprocationof the aforesaid stem 4.

Fig. 6 diagrammatically illustrates another form of rocker R1", similarto R except that the arms RI are here extended to serve four instead oftwo scavenging valves; two of said four, S2 and S3, being shown in thefigure. The difference in travel between the portion of the arm abovestem S2 and that above S3 is compensated for by a spiral spring D, thestiifness of which is less than the initial load on the valve spring,spring D collapsing against itself after a given movement of arm R1" andthereafter acting as a rigid member for depressing the valve-stems S3,thereby taking up the lost motion between the arm and stem withoutclatter.

The tappet means, itself consists of a depending sleeve 5 fixed with thehousing H of a cam shaft C and having a cap 6, said sleeve beingfastened by means such as similar flanges, 5' and 6 respectively. Withinthe bore of sleeve 5 is slidably located a spring cage I, closed at thetop by a spider element 8 having annularly arranged apertures 8', whichserve to lighten the piece and provide spannerwrench holes fortightening it. Spider 8 has an axial bore 8 guiding a tubular stem 4whose upward movements are limited by a flange or abutment 4' whichshoulders against the underside of the spider. The cap 6 has a bushing 9closely fitted to stem 4. The fit of said stem in said bushing isfurther sealed against oil leakage by packing material IIJ pressedbetween bushing 9 and a washer II by means of a compression spring I2.The spring I2 also functions to depress the parts I and 8 which actionkeeps a roller I4 resiliently contacting the face Cb of a cam Ca. Thespring-cage 'I has a bottom wall I between which latter and the flange4' is compressed a power or tappet spring I3. Spring cage I provides,beneath the bottom I an open ended chamber 7" wherein is mounted thecam-roller I4 having a pintle' I5 stationary in sleeve 1 but extendingto dispose flat portions I5 for reciprocative movement in slots 5",formed in the depending skirt of the outer sleeve 5. The bottom edge ofthe said sleeve may be cut away at a: if necessary for clearance for thecam Ca upon which the roller I4 rides. The said roller is prevented fromleaving its associated parts, in the event sleeve 5 and its attachedparts, or cam shaft C is removed from the engine, by machining the skirtof the sleeve 5 to form the walls 5w (Fig. 5) through which is passed acotter-pin I6 that shoulders under the ledge I5" formed in either one orboth of the flats I5 of the rollerpintle IS.

The housing H is exposed to the splash of crankcase oil, so that theseveral elements of the tappet assembly are kept lubricated throughsuitable apertures and bores a, b, and c in the several elements.

Adjustment of the clearance between the tappet and rocker and stem S isprovided by the threaded push rod 2 and its associated nut 3. Also, oneof the arms RI is provided with a screw I1 and a suitable nut I8 foradjusting the clearance between the stem and arm to permit obtainingequal clearance for the two stems.

Because of the control of the scavenging timing exerted by the cylinderpressure, cam Ca may be made symmetrical, so as to properly operate thescavenging valves in either direction of rotation of shaft C. As therise of the cam encounters the roller I4, the roll and its attachedparts, shaft I5, and sleeve or cage I, are forced upwardly, but becauseof the pressure normally obtaining in the engine cylinder, and theconsequent resistance to movement of valve stems S, stem 4 will beprevented from moving, and spring I3 will be compressed, storing energyfor later actuation of the valves. After the opening of the exhaustport, in the normal operation of the engine, the cylinder pressurefalls, and when it becomes equal to, or slightly less than that inmanifold M, the total resistance to movement of the valves becomes lessthan the force exerted by the compressed spring I3, and the valves areopened. This takes place sometime during the contact of roller I4 withthe dwell portion Cb of cam Ca. At the proper time in the cycle, thedwell portion passes out from under roller I4, and the roller, cage,spring, and stem 4, all move downwardly, allowing the valves to close inthe ordinary manner. The point at which the rise of the cam strikes theroller is therefore not critical, and since the normal opening point ofthe valves is slightly nearer bottom dead-center in the travel of theengine piston, than the closing point, the fall of the cam, for rotationin one direction, may be the rise for rotation in the oppositedirection, and the fact that it raises the roller a little earlier inthe cycle than the desired opening point of the valves is of noconsequence in the operation of the engine. Of course the parts might bearranged within the contemplation of the invention so that the rise ofthe roller I4 would correspond accurately with the opening of theexhaust port, if desired, spring I3 then allowing the valves to remainclosed during part of the exhaust period, or until the cylinder pressurefalls to or below that of the scavenging air.

In the event that it is desirable to provide an additional valve orvalves in the engine cylinder,

it may be done by lengthening either or both of arms R1 and using theconstruction shown in Fig. 6, with the spring D interposed between thearm and stem S3.

The above being a complete description of an illustrative embodiment ofthe invention, what is claimed as new and desired to be secured byLetters Patent of the United States is:

1. In a valve actuating mechanism the combination of a cam, a rocker armand connections between said cam and said arm arranged to actuate saidarm, a fulcrum for said arm, and a plurality of valve stems actuatedfrom said rocker arm, arranged for equal movement, but unequally spacedfrom said fulcrum, resilient means urging said stems in one directionone of said valve stems relatively near said fulcrum being substantiallyin contact with said rocker arm in the position of the partscorresponding to the closed position of said valves, and another of saidvalve stems relatively distant from said fulcrum being substantiallyspaced from said rockerarm whereby t'o-receive only an amountof-movement substantially equal to that of the above mentioned valvestem, and a. spiral spring interposed between the-last mentioned stemand said rocker arm and proportioned so that the coils thereof close andform a positive actuating means between said rocker arm andsaid valvestem at a point in the movement of said rocker arm such that theremaining movement of the rocker arm will impart movement to the secondvalve substantially equal to that of the first valve.

2'. In a tappet mechanism the combination of a camhaving a rolleractuating surface and a cam follower including a guldemember having asubstantiallycylindrical bore and'provided with an axial slot arrangedsubstantially on a diameter of saidbore perpendicular to the directionof movement of said roller actuating surface, a plunger guided in saidbore and having a roller receiving recess, said plunger-being providedwith a bore transverse to said recess, a pin in said bore and having areduced end portion extending into said slot to prevent rotation of saidplunger in said cylindrical bore while permitting axial displacement ofsaid plunger, and a roller journaled on said pin within said recess andcooperating with said roller actuating surface.

3. In a tappet mechanism for a valve subject to a varying resistance tomovement, the combination of a cam for moving said valve, a followercooperating with said cam and including a sleeve, guiding means for saidsleeve providing a bore in which said sleeve is slidable, a camcontacting element at one end of said sleeve, and a resilient elementarranged to urge said sleeve in a direction to maintain said contactingelement in contact with said cam, a valve actuating rod guided in saidguiding means and projecting into said sleeve, an abutment on said rodwithin said sleeve, a stop member on said sleeve and positioned tocooperate with said abutment to prevent removal of said rod from saidsleeve, and a resilient element in said sleeve and acting in a directiontoyieldingly maintain said abutment against said stop, and to yield andpermit movement of said sleeve under the influence of said cam at suchtimes as there is sumcient resistance to the movement of said valve toprevent actuation thereof through said resilient element, and tomaintain said abutment against said stop and to actuate said valve atsuch times as there is insufficient resistance to the movement of saidvalve to cause said resilient element to be compressed.

4. In a tappet mechanism for a valve subject to varying resistance tomovement, the combination with a valve, of a relatively light valvespring arranged for operating said valve in the direction of saidresistance, a cam for moving said valve, a follower cooperating withsaid cam, and connections from said follower to said valve includingresilient means positioned between said cam follower and said valve, andarranged to receive and absorb the full movement of said follower causedby said cam at times when said valve strongly resists opening, and tooperate said valve upon reduction of the resistance to the operation ofsaid valve below an amount sufficient to cause said resilient means tobe compressed, said resilient means being of a strength superior to saidrelatively light valve spring, whereby said valve spring will notinterfere with operation of said valve by said cam through saidresilient means,

except-when assisted by the above mentioned resistance to: movement ofsaid valve.

5. In a tappet mechanism for a valve subject to varying resistanceto-movement, the combination with a valve, of a relatively light valvespring arranged: for operating said valve in the direction of' saidresistance, a camfor moving said valve, a follower cooperating with saidcam and including a sleeve,means for guiding said sleeve forreciprocatingmovement in response to movement of said cam, a valveactuating rod extending into said sleeve, and a tappet spring disposedin said sleeve and" arranged to-exert resilient pressure against saidrod, said spring being disposed between a portion of said sleeve andsaid rod so astoconstitute the actuating means for said rod wherebyto becompressed and to receive energy from said cam at such times assufficient resistance i'soffered' tomovement of said valve and rod tocause said tappet spring to be compressed, F

and to release said energy and move' said valve upon reduction of saidresistance below such an amount, said tappet spring being of a strengthsubstantially greater than said valve spring.

6. In a tappet mechanism for a valve subject to varying resistance tomovement, the combination with a valve, of a relatively light valvespring arranged for operating said valve in the direction of saidresistance, a cam for moving said valve, a follower cooperating withsaid cam and including a sleeve, means for guiding said sleeve forreciprocating movement in response to movement of said cam, a Valveactuating rod extending into said sleeve, an abutment on said rod withinsaid sleeve, a stop on said sleeve positioned to prevent withdrawal ofsaid rod from said sleeve, and a tappet spring within said sleeve and.compressed between a portion thereof and said valve actuating rod toyieldingly maintain said abutment in contact with said stop, saidtap-pet spring being of a strength such that said valve spring does notinterfere with operation of said valve except when assisted by the abovementioned resistance to movement of said valve, but to yield and permitmovement of said sleeve in response to said cam independently of saidvalve actuating rod when the combined force of said resistance and saidvalve spring exceeds the strength of said tappet spring.

'7. In an actuating mechanism for a valve subject to varying resistanceto movement, the combination with said valve, of a cam, a cam follower,and connections from said follower arranged to operate said valve, saidconnections including a spring interposed between said follower and saidvalve, and having a capacity for yielding at least equal to the fulllift of said cam at the point of introduction of said spring into saidconnections when said resistance is at a maximum, and of a stiffnesssuflicient to actuate said valve through the full range of movement ofsaid valve when said resistance to movement is at a minimum, wherebysaid cam may move said valve through its full range of movement uponcessation of said maximum resistance to movement, and whereby said cammay move said follower through its full range of movement Without movingsaid valve at times of maximum resistance to movement of said valve.

8. In a tappet mechanism for a valve subject to varying resistance tomovement, the combination with a valve, of a relatively light valvespring arranged for operating said valve in the direction of saidresistance, a cam for moving said valve, a follower cooperating withsaid cam and including a sleeve, guiding means for said sleeve providinga bore in which said sleeve is slidable, a cam contacting element at oneend of said sleeve, and a resilient element arranged to urge said sleevein a direction to maintain said contacting element in contact with saidcam, a valve actuating rod guided in said guiding means and projectinginto said sleeve, an abutment on said rod within said sleeve, a stopmember on said sleeve and positioned to cooperate with said abutment toprevent removal of said rod from said sleeve, and a resilient element insaid sleeve and acting in a direction to yieldingly maintain saidabutment against said stop, said element being of a strength such thatsaid valve spring does not interfere with operation of said valve exceptwhen assisted by said resistance to movement of said valve, but to yieldand permit movement of said sleeve under the influence of said cam atsuch times as there is resistance to the movement of said valve.

9. In a tappet mechanism for an intake valve for an internal combustionengine having an exhaust port opened by extreme outward travel of thepiston thereof, the combination with a valve of a relatively light valvespring arranged to close the valve, a cam for moving said valve, afollower cooperating with said cam, and connections from said followerto said valve including resilient means positioned between said camfollower and said valve, and arranged to receive and absorb the fullmovement of said follower caused by said cam in the event that saidvalve is prevented from moving, said cam having a rise portion, a dwell,and a fall portion, said portions being symmetrical about a point ofcontact of said follower with said cam representing the extreme outwardtravel of the piston of said engine, whereby the action of said valvewill be coordinated with the opening of said exhaust port in eitherdirection of operation of said engine.

JOHN LEONARD TAYLOR.

